Aortic intima of the rat in various phases of hypertension

Abstract

Intimal changes of rat thoracic aorta were reviewed in early and late phases of two selected models of hypertension: (1) aortic ligation, a model associated with high plasma renin level in the early phase, but normal or low plasma renin levels in the late phase of hypertension; (2) high salt diet and unilateral nephrectomy, a model known to result in slowly rising blood pressure associated with continuously low levels of plasma renin. In hypertension produced by aortic ligation, the aortic endothelium showed an increased permeability to horseradish peroxidase in the early phase which was not observed in the late phase. Endothelial cells were markedly hypertrophic and contained a cytoplasmic contractile apparatus in the early phase, while they were smaller and showed less prominent microfilaments in the late phase of hypertension. In the late phase, accumulation of connective tissue matrix was noted, in addition in the subendothelial layer. In hypertension induced by high salt diet and unilateral nephrectomy, there was some endothelial cell hypertrophy at the early phase, but changes in permeability and in cytoplasmic contractile filaments were not detected at any phase. The most prominent morphological finding in this model was a progressive accumulation of connective tissue matix in the subendothelial layer. These data indicate that the aortic endothelium may react differently to varying hypertensive stimuli and may adapt to high levels of blood pressure.